:term:`CFOUR_LOCK_ORBOCC <CFOUR_LOCK_ORBOCC (CFOUR)>`
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      This keyword is used by the SCF program to determine if the orbital occupancy (by symmetry block) is allowed to change in the course of the calculation. ON (=1) locks the occupation to that set by the keyword :term:`CFOUR_OCCUPATION <CFOUR_OCCUPATION (CFOUR)>` (or the initial guess if omitted); OFF (= 0) permits the occupation to change. (Default : 1 if the occupation is specified with :term:`CFOUR_OCCUPATION <CFOUR_OCCUPATION (CFOUR)>` and for second and later steps of optimizations; 0 if :term:`CFOUR_OCCUPATION <CFOUR_OCCUPATION (CFOUR)>` omitted.)

      * **Type**: :ref:`boolean <op_c_boolean>`
      * **Default**: false